1. Field of the Invention
The present invention relates to a rework process for a photoresist film over a substrate having an antireflection silicone resin film and a photoresist film over the silicone resin film.
2. Description of the Related Art
With a tendency of realizing high integration and high-speed of LSI, a finer pattern rule has been demanded in recent years. The lithography technique with optical exposure, which is used for general purpose at present, is reaching an inherent limiting resolution derived from a wavelength of a light source.
There is widely used optical exposure using g line (436 nm) or i line (365 nm) of a mercury-vapor lamp as a light source for lithography when a resist pattern is formed. It has been considered that a method of using an exposure light with a shorter wavelength is effective as a means for obtaining a further finer pattern. For this reason, KrF excimer laser (248 nm) with a short wavelength is used as an exposure light source instead of i line (365 nm), for example, for mass-production process of a 64 M bit DRAM processing method. However, a light source with far shorter wavelength is needed to manufacture DRAM with integrity of 1 G or more which needs still finer processing techniques (for example, a processing size is 0.13 μm or less). Accordingly, lithography with ArF excimer laser (193 nm) has been particularly examined.
There is a multilayer-resist process to form a pattern on a substrate with such lithography techniques.
For example, to prevent deterioration of a resist pattern due to halation or a standing wave, a method of providing an Anti-Reflecting Coating between a substrate and a photoresist film is known.
Furthermore, to form a pattern with a high aspect ratio on a stepped substrate, a method of using a substrate with an organic film thereon, a silicon-containing film thereon, and a photoresist film thereon is known (for example, see J. Vac. Sci. Technol., 16(6), November/December 1979).
In view of enhancing resolution, a thinner photoresist film is desirable. On the other hand, in view of obtaining good embedding characteristics for substrate steps and high etching resistance when a substrate is etched, a thicker photoresist film is desirable. Then, three stacked layers can have a layer with good embedding characteristics for substrate steps and high dry etching resistance; and a layer with high resolution, separately. Consequently, it becomes possible to form a pattern with a high aspect ratio on a stepped substrate.
As the silicon-containing film, for example, a Spin On Glass (SOG) film is used. Many SOG films have been suggested.
To form a pattern on such a substrate, first, the pattern circuit area of a photoresist film is exposed and then developed with a developer to form a resist pattern on the photoresist film. Second, a pattern is formed on an antireflection film or an SOG film by using the photoresist film as a mask. In this way, the resist pattern is transferred sequentially, and finally, a pattern is formed on a substrate.
In the above process, formation of a resist pattern can fail because striation is generated when a resist solution is applied, or deviation is generated in the resist pattern after exposure. In such a case of failure, transferring a pattern down to a substrate with a deviated resist pattern produces a failed substrate and also wastes time and manpower expended for producing the substrate.
Then, when formation of a resist pattern fails, the so-called rework process for a photoresist film is conducted as follows: A photoresist film with a deviated resist pattern and an antireflection film or an SOG film under the photoresist film are removed. Then again, an antireflection film or an SOG film is formed, and a photoresist film is further formed thereon.
However, such a conventional rework process for a photoresist film has problems that it is cumbersome and it costs too much.
Furthermore, forming a resist pattern on a reworked photoresist film can provide a bad resist pattern.